1. Field of the Invention
The present invention relates to a method of manufacturing window frames from plastic sections. The plastic sections for always two window frames to be welded at a distance one above the other are placed in the double welding heads of a horizontal four-head welding machine, wherein the double welding heads are arranged in pairs on a displaceable carriage so as to be shiftable relative to each other. The plastic sections are then clamped in the welding machine and are welded. After at least partial cooling, the welded window frames are released and removed.
The present invention also relates to an apparatus for carrying out the above-described method.
2. Description of the Related Art
For manufacturing window frames of plastic sections, welding machines are used which are constructed as four-head welding machines and assume, for example, a horizontal position. The individual sections are placed from above into a horizontally operating four-head welding machine, are clamped in the machine and are welded together under pressure and heat. After welding, the frame is removed upwardly, for example, by hand, and is transferred to a horizontal transport device which conveys the frame to a welding bead cleaning or trimming machine.
However, it is also known in the art to push the welded frame released from the clamping devices of the four-head welding machine in its horizontal position out of the four-head welding machine. The frames can be pushed out either by means of a special pushing device or by two welding heads. Also in this case, the welded frames are conveyed by a transport device to the welding bead cleaning or trimming machine in which the individual corners of the welded frames are freed from the welding beads.
In a plant for manufacturing frames of plastic material, which may be casements as well as door and window frames, wherein the plant is comprised of horizontal four-head welding machine and a horizontal welding bead cleaning or trimming machine, the output of the plant is dependant on the slowest unit, i.e., the four-head welding machine because heating of the plastic sections for the welding procedure and cooling of the welding seams takes a relatively long time. This means that the capacity of the welding bead cleaning or trimming machine cannot be fully utilized.
In order to increase the output of such a manufacturing plant, it is known in the art to construct the individual welding heads of the four-head welding machine in the form of so-called double welding heads. In such a four-head welding machine with double welding heads, the individual sections for two window frames are successively placed in the machine and are simultaneously welded together to form window frames. However, the removal of the finished welded window frames takes place manually in this type of four-head welding machine because the lower frame can only be released for removal and taken out once the upper window frame is no longer in the four-head welding machine. Also in this case, the removed window frames are transferred to a transport device which conveys the frames to a subsequently arranged welding bead cleaning or trimming machine. By removing the finished welded window frames manually, the actual capacity of a four-head welding machine with double welding heads is not utilized in an optimum manner, so that the capacity of such a manufacturing plant is relatively low.